Denitrogenation by Adsorption of Pyridine on Ni/Support Adsorbents

Abstract

In this work we have carried out the adsorption of pyridine using three different supports (activated carbon, SiO 2 and γ-Al 2 O 3 ). After choosing the best support, due to its higher adsorption capacity, we have impregnated the support with nickel at three different concentrations (2, 4 and 6% w/w) by wet impregnation to study the adsorption of pyridine by π-complexation. All the samples (supports and adsorbents) were characterized by N 2 adsorption-desorption by the BET method and electrophoretic migration. The experimental results, for the three different supports, show that the adsorption capacity is better for γ-Al 2 O 3, due to its higher isoelectric point. With the incorporation of nickel, no better adsorption capacities are observed, due that the nickel incorporation diminish the zero point charges of the adsorbents. Adsorption, denitrogenation, nickel, pyridine. e-mail: patricio.baeza@pucv.cl Keywords: INTRODUCTIONCrude oil is the largest and most widely used source of energy in the world and projections assure that this will continue until at least 2050. Overexploitation of existing fields, has led to crude oils known as "Barrel Fund", composed of high molecular weight hydrocarbons which are of lower quality, as they are much heavier and therefore difficult to purify in the petroleum refining industry. The combustion of petroleum containing nitrogen compounds emits NOx into the atmosphere, which directly contributes to the production of acid rain and Photochemical Smog. Therefore, environmental regulations are becoming more stringent with regard to the maximum level of nitrogen molecules that petroleum may contain; this has caused refiners to seek new methods that allow them to eliminate nitrogenous molecules. These nitrogen containing molecules are more resistant to the existing process used in the refining industry to remove them. This hydrotreating process is called hydrodenitrogenation (HDN) and it operates at elevated temperatures and pressures, which are efficient in removing simple nitrogen molecules, but not for the removal of "refractory molecules". Nitrogenous compounds present in the petroleum may vary depending on the origin of the oil field. Despite this, the predominant compounds consist of substituted pyrrole and pyridine, which containing aromatic rings of 5 and 6 members, respectively 1 . At present, petroleum is composed of alkylated nitrogenous organic molecules, on some part of the aromatic ring, which are refractory to the HDN process 2,3 .It should be noted that the catalysts used in petroleum refining for the HDN reaction are Ni-Mo/γ-Al 2 O 3 or Co-Mo/γ-Al 2 O 3 catalysts, where Co and Ni promote the activity of MoS 2 , but an important point is that these catalysts are also active in the hydrodesulfurization (HDS) reaction, and furthermore, both reactions are carried out in the same reactor with an unique catalyst, and in the case of nitrogen containing compounds, their removal is highly recommended to ensure successful HDS. It is these nitrogen compounds that inhibi...

Simultaneous Adsorption of 4,6-Dimethyldibenzothiophene and Quinoline over Nickel and Boron Modified Gamma-Al2O3 Adsorbent

“…On this matter, the incorporation of nickel in different porous materials has been widely studied [7,24,25], due to the high adsorption capacity of this metal on diverse pollutants. However, in our previous work [3], we have shown that the incorporation of 4% nickel on alumina decreases the adsorption capacity of pyridine, due to the formation of NiAl 2 O 4 . On the other hand, the incorporation of boron has shown an improvement in the activity of HT catalysts, which is mainly associated with the modification of the acidity and dispersion of the active metals [26,27].…”

“…In order to economize the desulfurization or denitrogenation processes, other milder methods must be developed. In this regard, several research groups have studied the elimination of these types of molecules by adsorption [3][4][5][6][7], which, unlike HT reactions, is carried out at ambient temperature and pressure. Despite there being a wide variety of solids used as adsorbents, alumina is one of the main supports used in HT reactions [8][9][10][11][12][13] and has shown the capacity to remove sulfur and nitrogen compounds simultaneously by adsorption, as described by Kim et al [4].…”